The present invention relates to method and apparatus for making hollow seamless links for use in jewelry and, more particularly, to method and apparatus for making hollow seamless gold links for use in a chain, for example, a gold chain made in the form of a rope (a "gold rope chain").
U.S. Pat. No. 4,503,664 (Allazzetta et al.), which is incorporated herein by reference, discloses a rope chain machine which manufactures chains by cutting gold solid wire fed to the machine into successive pieces and forming the cut pieces into open rings on a movable conveyor pin. The rings, which also are known as "links", are combined in a known manner to produce the completed rope chain.
Traditionally, a gold chain is manufactured from 10KT, 14KT, etc, gold solid wire which generally results in a relatively heavy chain. One method for reducing the weight of a chain is to flatten each link prior to assembly. Another method is to construct a chain with hollow links.
A chain made of hollow links or rings, hereinafter "hollow chain", may be made by forming a thin sheet of gold alloy around a wire core made of another material (hereinafter referred to as "the non-gold core"), for example, aluminum, steel or copper. The gold alloy sheet and the non-gold core are drawn through a dial to form a wire which has a gold exterior surface and a non-gold inner core. The resultant wire contains a seam, as will be described below. Individual links made from this wire are produced by various methods. One method is to curl the wire around a rod so as to take on a spring-like form whereby the spring-like wire is cut along the length of the rod to produce open links. The links are then flattened.
As previously stated, the resultant wire contains a seam, that is, the gold alloy sheet does not completely encompass the entire circumference of the non-gold core wire, as shown in FIG. 1 of the drawings, and thus, the non-gold core material remains visible after the gold alloy is folded around the wire (or rather, the non-gold core material is exposed to air along the seam). It is generally necessary for the wire to have a seam to properly carry out the non-gold removal process (as will be described). However, because the existence of a seam adversely affects each link's appearance, thus substantially diminishing the resultant chain's overall appearance, it is essential that each link be made to have its seam located on the inner circumference thereof. In other words, a seam must be located on the interior side of the link so that it will not be exposed, i.e., visible, on the completed product.
Once a chain is manufactured, the non-gold core of each link must be removed to produce the "hollow" chain. Currently, it is known to remove a non-gold core material, such as aluminum, copper or steel, from a gold chain by dissolving the non-gold core in acid. Of course, such an acid does not dissolve the exterior gold-alloy surface of the links. When the non-gold core dissolves, gases are produced which escape through the seam of the link and, although it is appreciated that the existence of a seam in each link provides for the removal of the inner cores, the required seams cause production of hollow chain to be difficult because these seams must always be located on the inner circumference of the links in order to not degrade the appearance of the completed product. Given the relatively small size of a link, production of links with seams on their inner circumference is relatively difficult, or, at best, substantially limits the number of practical methods of producing such links. Furthermore, the existence of a seam reduces the link's overall strength, for example, by reducing the link's ability to keep its shape when subject to external forces, e.g., during ordinary handling or during formation of the link.